Production of alkyl benzenes



Filed June 2. 1947 Patented Dec. 12, 1950 PRODUCTION F ALKYL BENZENESWalter A. Schulze, Bartlesville, Okla., assignor to Phillips PetroleumCompany, a corporation of Delaware Application June z, 1947, sei-iai No.751,937

- 'I Claims. l

'I'his invention relates to the production of high molecular weightalkyl aromatic hydrocarbons. One embodiment of this invention relates toa two-step catalytic process for manufacturing alkyl benzenes. Aspecific embodiment of this v"invention relates to a continuouscatalytic process wherein substituted and/or polynuclear aromaticconstituents in a catalytically cracked naphtha fraction are alkylatedwith high molecular weight straight and branched chain oleiins containedin the said fraction to produce high ooiling alkylate mixtures vwhichare subsequently admixed with a molar excess of benzene therebyeffecting side chain transfer from the said high boiling alkylatemixture to the said benzene.

One prior method for the alkylation of aromatics with high molecularweight olens discloses the use of an olefin concentrate comprising afraction of a catalytically cracked naphtha containing substantialproportions of high molecular weight straightand branched-chain olefinsas the alkylating reactant for aromatic hydrocarbons in the productionof alkyl benzenes. While numerous advantages are realized by operatingin this manner, certain diiliculties are inherent in the process.Cracked naphtha fractions of the type employed as alkylating reactantsin the above mentioned method contain, in addition to the -highmolecular weight oleiins, certain aromatic constituents comprisingnaphthalenes,'alkyl and polyalkyl benzenes, and the like. The proportionof these aromatic constituents in the fraction is usually at least equalto and generally greater than that of the high molecular weight oleiinscontained therein. Therefore, when employing such a fraction as the.alkylatng reactant for, say, .benzene in the production of alkylbenzenes, a competing reaction occurs wherein the residual aromaticconstituents condense with the olefins present to produce undesirablehigh boiling alkylates. While the high boiling alkylates so formed maybe separated in the fractionation of the product, their formationconsumes a substantial amount of the ole.- fins and proportionallydiminishes the yield of desired product.

I have now discovered a process for the production of alkyl benzeneswhereinjthe advantages realized from the use of the low cost oleiinconcentrates derived from catalytically cracked naphthas are retainedand the dimculties hereinbefore mentioned are`substantially reduced orentirely eliminated. The method of my invention comprises the followingsteps: (a) frac'- tionating a catalytically cracked naphthato pro- (Cl.26o-871) duce a cut comprising olens of at least seven and not more thaneighteen carbon atoms to the molecule, in admixture with aromatic andparamnlc constituents boiling in the same range; (b) contacting saidfraction with an alkylating catalyst under conditions for thecondensation of the oleiins present with aromatic constituents toproduce high boiling alkylate mixtures; (c) separating and removingparafilnic and other hydrocarbons previously associated with theoleilns; (d) admixingthe alkylate with a molar excess of benzene andcontacting with an alkylating catalyst under conditions for transfer ofthe high molecular weight alkyl group or groups added in the alkylationstep from the high boiling alkylate `to the benzene; (e) separating andremoving unreacted benzene for recycle to the side chain transfer step;(f) separating and removing aromatic constituents recovered from thehigh boiling alkylate and discharging alkyl benzenes as product.

One object of this invention is to provide a process for the productionof high molecular weight alkyl aromatic hydrocarbons.

Another object is to provide a two-step catalytic process for themanufacture of alkyl benzenes.

Another object is to provide a two-step continuous catalytic process forthe production of alkyl benzenes whereby the aromatic hydrocarbonspresent in a cracked .naphtha fraction are alkylated with olenscontained in the said naphtha' fraction and the resulting high boilingalkylate mixed with a vmolar excess of benzene thereby eiectingsidegchain transfer from the said high boiling alkylate to the saidbenzene. Still another object of this invention is to provide a processfor the production of :alkyl benzenes suitable for use as detergentintermediates.

Other objects and advantages will become apparent to those skilled inthe art from the accompanying discussion and description.

A signicant feature of the present process lies in the utilization ofthearomatic constituents of the feed stock as carriers for the olefins fromthe alkylation step to the side-chain transfer step. According to theprecepts of my invention, alkylation of the aromatic nuclei proceeds toahighy degree when the reaction time is short, polyalkylation often beingthe lpredominant rel action. Since the residual aromatic constituents inthe feed stock comprise principally substituted period of contact withan alkylation catalyst and in the presence of unalkylated nuclei,transfer of alkyl groups from the polyalkylate to the unalkylated nucleitakes place. those groups containing the larger number of carbon atomsbeing principally affected.

Thus' by contacting the aromatic-olefin mixture comprised in the feedstock with an alkylating catalyst for a short time, generally betweenfive and 40 minutes and preferably between 10 and l minutes,condensation of oleilns with the residual aromatic constituents occursto produce a high boiling alkylate in which the aromatic nuclei aresubstituted by one or more straight or branched chain alkyl groups inaddition to substituent alkyl groups containing a lessnumber of carbonatoms previously present. This high boiling productin admlxture with amolar excess of benzene is contacted with an alkylating catalyst for alonger period of time. generally from 20 to 60 minutes. but preferablyfrom 25 to 45 minutes. Under suitable conditions, sidechain transferfrom the polysubstituted molecules of the high boiling alkylate to theunalkylated nuclei of the benzene is effected.

By operating in this manner, the losses incurred from formation ofundesirable high boiling alkylates which were noted in previousoperations employing highly oleilnic naphtha fractions as alkylatingagents are eliminated or substantially reduced. At the sameV timeoleilns of the feed stock are utilized to a high degree in theproduction of desirable alkylates. thus providing economic advantages ofa major order. 4

Further advantages of the present invention will be apparent from anexplanation of the accompanying drawing in which is shown a diagrammaticillustration for one specific embodiment of my process. While thedrawing and explanation relates to the use of liquid type catalysts suchas boron fluoride compositions, this particular embodiment is selectedmerely for simplicity in explanation, and is not limitingto the scope ofthe disclosure. Referring to the drawing, a charging stock comprising ahigh boiling naphtha or gas oil is introduced through line Ill into acatalytic cracking process I2 which may preferably be of a Cycloversiontype in which, after preheating, the feed stock is combined with hightemperature steam diluent introduced through line Il and passed over ailxed bed bauxite type catalyst maintained at a temperature in the rangeof 900 F. to 1200 F. See article by Schulze et al., Oil and Gas Journal,April 13, 1944. In this type of unit the high boiling charging stock iscatalytically cracked under non-polymerizing conditions to form acracked naphtha characterized by its high content of unusually stableolefins having from '7 to 18 carbon atoms per molecule, and of aromaticand paramn hvdrocarbons. In the interest of simplicity in the drawing,catalyst chambers, fractionating and stabilizing columns, and the likewhich are elements of the cracking process are not shown in detail.their design and arrangement being-conventional in nature.

The product from this unit is discharged through line Il to fractionatorIl where lightin admlxture with aromatic and paraflinic hydrocarbons isconveyed through line 24 to alkylation zone 26 where it is'contactedwith an alkylating catalyst which may suitably be a liquid complex orcomposition of boron fluoride under conditions such that the aromaticconstituents are condensed with the high molecular weight olefinspresent. Other catalytically or thermally cracked naphthas may be usedto prepare the desired charge to said alkylation zone. When operatingwith liquid type catalysts more effective contact is obtained bysuitable agitation of the system by a mechanical stirrer 28. Also. sincecatalysts of this type are high density materials, it is desirable thata recycling catalyst circulation be provided from the bottom of thereactor through line SII.

From alkylation zone 26 the eliluent is directed through line 32 tocatalyst separator 34 where it is separated by gravity into catalyst andhydrocarbon phases. The heavier catalyst phase is removed through line38 and restored to the circulating catalyst stream in line 30 while thehydrocarbon phase is discharged through line 38 to fractionator 4I. Hereparaiiinic hydrocarbons and unconverted aromatic constituents areremoved overhead via line 42 for storage or utilization elsewhere. Thisoverhead fraction often has an aromaticity of sufficient magnitude toqualify it as an eifective solvent naphtha.

The higher boiling residue comprising principally polysubstituted alkylbenzenes is conveyed through line 44 to mixing zone where it is combinedwith a molar excess of benzene drawn from storage 48 through line 50 andfrom recycle line 52. 'I'he mixture is conveyed through line Sito theside-chain transfer zone 56 where it is contacted with an alkylatingcatalyst which, in this speciflc embodiment, comprises a liquid typecatalyst such as was employed in the alkylation zone 26. The volume ofthe reactor used for the side-chain transfer step of the process islarger than the alkylation reactor by a sufilcient amount that with aflow rate which provides a contact time of 10 to l5 minutes in thealkylation zone. a contact time of 30 to 45 minutes is obtained in theside-chain transfer zone. Effective contact with the catalyst isobtained by agitation with mechanical stirrer 5l and by circulation ofthe catalyst through line Bl. Conditions in the side-chain transfer zoneare regulated in a manner such that transfer of straight and branchedchain alkyl groups added in the alkylation zone from the polyalkylate tothe benzene is enacted.

From the side-chain transfer zone the eilluent is conveyed through line82 to separator 6l from which the heavier catalyst phase is removedthrough line 66 to be restored to the circulating catalyst stream inlin/ett. Thehydrocarbonphase is passed through mie sa to the debenzemzmgco1- umn 10 where unreacted benzene is removed overhead via line t2 forrecycling to the sidechain transfer zone\ through mixing system I6. Thedebenzenized stream is then passed through line 12 to fractionator 'Ilwhere the aromatic hydrocarbons from which the high molecular weichtstraightand branched-chain alkyl groups were removed in the side-chaintransfer zone are separated and discharged through line 18 for storageor utilization elsewhere. The aromaticitv of this lower boiling fractionis very high. often beine as much as from to 90 per cent, thus providinga valuable source for very high solvent power solvent naphthas. Crudealkyl benlenesaredischargedvialineutofractionator Il which maypreferably be operated under reduced pressure. The alkyl benzene productis removed through line l2 and high boiling residues discharged via lineIl. In some instances these high boiling products, which compriselargely polyaikyl benzenes, may be recycled to the sidechain transferzone through line not shown for further treatment.

Aikylation of the residual aromatic compounds in the feedstock with thehigh molecular weight olefins contained therein is accomplished readilyand can be effected in the presentof a catalyst of amore lower activitythan that employed in the side-v chain transfer step. A preferred methodof operation therefore is to convey catalyst previously employed in theside-chain transfer step from line 06 via line 86 for introducing intoline 30 as catalyst feed to the alkylation zone 20. When operating inthis manner, spent catalyst is removed from the alkylation zone via line88 and conveyed to regeneration zone 90. Regenerated catalyst togetherwith such make-up as needed. the said make-up being drawn from storage92 via line Sl, is introduced into the side-chain transfer catalystsystem via line 8B.

In the accompanying diagrammatic drawing reference to some of theequipment such as pumps, gauges, and other equipment which obviouslywould be necessary to actually operate the process have beenintentionally omitted. Only sufficient equipment has been shown toillustrate the process of the invention and it is intended that no unduelimitation be read into this invention by reference to the drawing anddiscussion thereof.

The catalyst to be employed in the alkylation and side-chain transferzones of my process is a liquid type such as anhydrous hydrogenfluoride; boron fluoride complexes or compositions, which complexes orcompositions may comprise boron fluoride and water, boron fluoride andphosphoric acid, boron fluoride and hydrogen fluoride or boron vfluorideand aqueous hydrogen fluoride. Highly effective results can also beobtained by the use of hydrofluoric acid as the catalyst in aqueoussolutions of 50 per cent or higher concentration.

Temperatures in the reaction zones will generally be in a range between60 and 140 F., and preferably between 80 and 125 F. The reactions can beeected without the use of superatmospheric pressures but itis usuallypreferable tov apply suillcient pressure to avoid vaporization of thecatalyst; for example, pressure of from 30 to 50 pounds per square inchgaugel is sumcient. The volume ratio of benzene to alkylate in theside-chain transfer step will be between 2: 1

and :1. preferably from 5:1 to 10:1. The volume ratio of catalyst tohydrocarbons in both the alkyltion zone and the side-chaintransferzonewill vary considerably depending upon the' particular catalyst andother yariablefactors, but usually a ratio in the range of 1:1 to 1:5 ineach zone is satisfactory.

The foregoing disclosure relates' particularly to the alkylation ofbenzene with oleflns from an olefin concentrate. However, the process isapplicable to the alkylation of aromatic hydrocarbons containing asubstituent alkyl group such as toluene. Polysubstituted benzenes suchas the xylenes may be employed in some instances although side-chaintransfer is less readily effected as the number of substituent alkylgroups appreaches that which exists in the polyalkyla'fe from thealkylation step.

Example A high-boiling naphtha was subjected t catalytic cracking by a"Cycloversion process. The product was fractionated to yield a cutboiling in the range 400 to 450 F. and comprising about 20 per cent highmolecular weight oleflns. A sample of the naphtha so prepared weighing1,652 grams was contacted with a catalyst consisting of 50 per centaqueous hydrouoric acid saturated with boron fluoride gas for a periodof 20 minutes at a temperature of 120-130 F. Fractionation of theeiiiuent yielded 435.7 grams of alkylate boiling above 690 F. Thisproduct was commingled with 765 grams of benzene and contacted with thecatalyst for a period of one hour, conditions being maintained asbefore. Fractionationl of the eluent yielded 310 grams of alkylateboiling in the range 550 to 680 F.

It is to be understood that this invention should not be unnecessarilylimited to the above discussion and description and that modificationsand variations may be made without departing substantially from theinvention or from the scope r of the claims.

I claim:

l. A two-step process for catalytically producing high molecular weightalkyl benzenes, which comprises fractionating l a catalytically crackednaphtha to produce a fraction containing olens having at least seven andnot more than eighteen carbon atoms to the molecule and alkylatablearomatic constituents; contacting said fraction with a liquid typealkylation catalyst in an alkylation zone under conditions such thatsaid olens react with said aromatica; separating effluent reactionmixture from said alkylation zone into a catalyst phase and ahydrocarbon phase in a separation zone; introducing said hydrocarbonphase into a fractionation zone, removing unreacted hydrocarbonspreviously associated with the olefin-aromatic containing fraction;mixing the resulting high-boiling alkylate with excess benzene in amixing zone, contacting resulting mixture in a side-chain transfer zonewith a liquid type alkylation catalyst under conditions to effectside-chain transfer from said high-boiling alkylate material tounalkylated benzene; separating eiliuent reaction mixture from saidside-chain transfer zone in a separating zone into a catalyst phase anda hydrocarbon phase and recovering high molecular weight monoalkylbenzenes from said hydrocarbon phase.

2. A two-step process for catalytically producing high molecular Weightalkyl benzenes, which comprises fractonating a catalytically crackednaphtha to produce a. fraction containing oleflns having at least sevenand not more than eighteen carbon atoms to the molecule and alkylatablearomatic constituents; contacting said fraction with a liquid typealkylation catalyst in an alkylation zone under conditions 'such' thatsaid oleflns react with said aromatics; separating eniuent reactionmixture from said alkylation zone into a catalyst phase and ahydrocarbon phase in a separation zone; introducing said hydrocarbonphase into a fractionation zone; removing unreacted hydrocarbonspreviously associated with the olefin-aromatic containing fraction;mixing resulting high-boiling alkylate material with excess benzene in amixing zone, contacting resulting mixture in a side-chain transfer zonewith a liquid type alkylation catalyst under conditions to effectside-chain transfer Y" from sala nigh-boiling alkylate material to un- 7alkylated benzene; separating eiuent reaction mixture from saidside-chain transfer zone in a separating zone into a catalyst phase anda hydrocarbon phase; recycling at least a portion of said catalyst phaseto saidl alkylation zone; introducing said hydrocarbon phase into adebenzenizing zone and removing unreacted benzene from` said hydrocarbonphase; introducing remaining hydrocarbon phase into a fractionationzone, removing low-boiling aromaticV constituents resulting from theside-chain transfer reaction in said transfer zone, introducingresulting alkyl benzene vmaterial into a second fractionation zone andremoving monoalkyl benzenes as a product of the process.

3. A two-step process for catalytically producing high molecular weightalkyl benzenes, which comprises fractionating a cracked naphtha toproduce a fraction containing oleflns having at least seven and not morethan eighteen carbon atoms to the molecule and alkylatable aromaticconstituents; contacting said fraction with liquid type alkylationcatalyst in an alkylation zone; maintaining temperature insaidalkylation zone in a range of 60 to 140 F.; maintaining pressure insaid alkylation zone suilicient to prevent vaporization of saidcatalyst; maintaining a volume ratio of catalyst to said fraction inalkylation zone in the range of 1:1 to 1:5; maintaining rate of flow ofsaid fraction and catalyst such that the residence time in saidalkylation zone is in the range of 5 to 40 minutes; separating eiiiuentreaction mixture from said alkylation zone into a catalyst phase and `ahydrocarbon phase in a separation zone; recycling at least a portion ofsaid catalyst phase to said alkylation zone; introducing saidhydrocarbon phase into a fractionation zone, removing unreactedhydrocarbons previously associated with the olefin-aromatic containingfraction; mixing resulting highboiling alkylate material with a molarexcess of benzene in a mixing zone, contacting resulting mixture in aside-chain transfer zone with a liquid type alkylation catalyst;maintaining temperature in s aid side-chain transfer zone in a range of60 to 140 F.; maintaining a pressure in said side-chain transfer zonesuiiicient to prevent vaporization of the catalyst; maintaining a volumeratio of catalyst to total hydrocarbon material in said side-chaintransfer zone-in range of 1:1 to 1:5; Vmaintaining a rate of flow ofreactants and catalyst such that residence'time in said side-chaintransfer zone is in range of 20 to 60 minutes; separating eiiiuentreaction mixture from said side-chain transfer zone into a catalystphase and a hydrocarbon phase in a separating zone; recycling at least aportion of said catalyst phase to said side-chain transfer zone andremaining catalyst phase to said alkylation zone; introducing saidhydrocarbon phase into a fractionation zone and removing unreactedbenzene from said hydrocarbon phase; introducing remaining hydrocarbonphase into a second fractionation zone, removing low-boiling aromaticconstituents resulting from the side-chain transfer reaction in saidtransfer zone. introducing resulting high-boiling alkyl benzene materialinto. a thirdA fractionation zone and removing monoalkyl benzenes as aproduct of theprocess.

4. A two-step process for catalytically producing high molecular weightalkyl benzenes. which comprises catalytically cracking a highboilingnaphtha by mixing the naphtha with preheated steam-and passing themixture at a temperature in the range 950 to 1050 F. at a -pres-:,ssgova sure of 'I5 toA 100 unds per square inch gauge over a fixedbed, a umina. type catalyst. iractionating the resulting cracked naphthato p roduce a fraction containing olefins having at least seven and notmore than eighteen carbon atoms to the molecule and alkylatable aromaticconstituents; contacting said fraction with va liquid type alkylationcatalyst in an alkylation zone: maintaining the temperature in saidalkylation zone in the range of 60 to 140\F.; maintaining pressure insaid alkylation zone sufficient to prevent vaporization of saidcatalyst; maintaining a volume ratio of catalystto said fraction inalkylation zone in the range of 1:1 to 1:5; maintaining a rate of iiowof said fraction and catalyst such that the residence time in saidalkylation zone is in the range of 5 to 40 minutes; separating eiiiuentreaction mixture from said alkylation zone into a catalyst phase and ahydrocarbon phase in a separation zone; recycling at least a portion ofsaid, catalyst phase to said alkylation zone; introducing saidhydrocarbon phase into a fractionation zone, removing unreactedhydrocarbons previously associated with the olefin-aromatic containingfraction; mixing resulting high-boiling alkylate material with a molarexcess of benzene in a m Xing zone, contacting resulting mixture in aside-chain transfer zone with a liquid type alkylation catalyst;maintaining temperature in said side-chain transfer zone,v

in the rangen: 60 to 140 F.; maintaining me pressure in said side-chaintransfer zone sufll.-

carbon material in said side-chain transferzone 1 in the range of 1:1 to1:5, maintaining the rate of iiow of reactants and catalyst such thatresidence time in said side-chain transfer zone is in the range of 20 to60 minutes; separating eiliuent reaction mixture from said side-chaintransfer zone into a catalyst phase and a hydrocarbon phase in aseparating zone; recycling at least a portion of said catalyst phase tosaid sidechain transfer zone and remaining catalyst phase to saidalkylation zone; introducing said hydrocarbon phase into a debenzenizingzone and removing unreacted benzene from said hydrocarbon phase;introducing remaining hydrocarbon phase into a fractionation zone.removing low-boiling aromatic constituents resulting from the side-chaintransfer reaction in said transfer sone. introducing resultinghigh-boiling alkyl benzene material into a second fractionation zone andremoving monoalkyl benzenes as a -product of the process.

5. A process as in claim 4 wherein the vcatalyst used is anhydroushydrogen fluoride.

6. A processas in claim 4 wherein the catalyst is a boron fluoridecomplex. Y

7. A process as in claim 4 wherein the catalyst used is hydroiiuoricacid of at least 50 per cent concentration.

WALTER A. SCHULZE.

REFERENCES CITED The following references are of record inthe le of thispatent:

UNITED STATES PATEN'I'S Number Name Date 42,001,907 Ipatieif May 21,1935 2,315,506 Danner et al. Apr. 6, 1943 2,343,870 Kaplan Mar. 14, 19442,349,211 Tulleners May 16. 1944 (ther references on following page)Number v 9 UNITED STATES PATENTS Name Date Bruner et al May 15, 1945Mattox Sept. 25, 1945 Carmody Mar. 19, 1946 v Schulze et al July 9, 1946Zerner et al. Dec.24, 1946 Friedman et al. Dec. 14, 1948 OTHERREFERENCES Simons, Potential Use Processes, Ind. and Eng. Chem., vol.32, No. 2 (Feb. 1940), pages 178-183 (6 pages).

`Schulze et al., Gas-Oil Cycloversion Process, Oil and Gas Jour., vol.42 (April 13. 1944),*pages 225, 6, 9, 30, 35 (5 pages).

1. A TWO-STEP PROCESS FOR CATALYTICALLY PRODUCING HIGH MOLECULAR WEIGHTALKYL BENZANES, WHICH COMPRISES FRACTIONATING A CATALYTICALLY CRACKEDNAPHTHA TO PRODUCE A FRACTION CONTAINING OLEFINS HAVING AT LEAST SEVENADN NOT MORE THAN EIGHTEEN CARBON ATOMS TO THE MOLECULE AND ALKYLATABLEAROMATIC CONSTITUENTS; CONTACTING SAID FRACTION WITH A LIQUID TYPEALKYLATION CATALYST IN AN ALKYLATION ZONE UNDER CONDITIONS SUCH THATSAID OLEFINS REACT WITH SAID AROMATICS; SEPARATING EFFLUENT REACTIONMIXTURE FROM SAID ALKYLATION ZONE INTO A CATALYST PHASE AND AHYDROCARBON PHASE IN A SEPARATION ZONE; INTRODUCING SAID HYDROCARBONPHASE INTO A FRACTIONATION ZONE, REMOVING UNREACTED HYDROCARBONSPREVIOUSLY ASSOCIATED WITH THE OLEFIN-AROMATIC CONTAINING FRACTION;MIXING THE RESULTING HIGH-BOILING ALKYLATE WITH EXCESS BENZENE IN AMIXING ZONE, CONTACTING RESULTING MIXTURE IN A SIDE-CHAIN TRANSFER ZONEWITH A LIQUID TYPE ALKYLATION CATALYST UNDER CONDITIONS TO EFFECTSIDE-CHAIN TRANSFER FROM SAID HIGH-BOILING ALKYLATE MATERIAL TOUNALKYLATED BENZENE; SEPARATING EFFLUENT REACTION MIXTURE FROM SAIDSIDE-CHAIN TRANSFER ZONE IN A SEPARATING ZONE INTO A CATALYST PHASE ANDA HYDROCARBON PHASE AND RECOVERIN GHIGH MOLECULAR WEIGHT MONOALKYLBENZENES FROM SAID HYDROCARBON PHASE.